/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
using System;
using Velocity4Net.Runtime;
using System.IO;
using System.Collections;
using Velocity4Net.Runtime.ResourceManage;
using Velocity4Net.Ctx;
using Velocity4Net.Errors;
using Velocity4Net.Runtime.Parse;
using Velocity4Net.Runtime.Parse.AST;
using Velocity4Net.Runtime.Directives;
using System.Text;


namespace Velocity4Net
{
    /**
     * This class is used for controlling all template
     * operations. This class uses a parser created
     * by JavaCC to create an AST that is subsequently
     * traversed by a Visitor.
     *
     * <pre>
     * // set up and initialize Velocity before this code block
     *
     * Template template = Velocity.getTemplate("test.wm");
     * Context context = new VelocityContext();
     *
     * context.put("foo", "bar");
     * context.put("customer", new Customer());
     *
     * template.merge(context, writer);
     * </pre>
     *
     * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
     * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
     * @version $Id: Template.java 778045 2009-05-23 22:17:46Z nbubna $
     */
    public class Template : Resource
    {
        /*
         * The name of the variable to use when placing
         * the scope object into the context.
         */
        private String scopeName = "template";
        private bool provideScope = false;

        private VelocityException errorCondition = null;

        /** Default constructor */
        public Template()
            : base()
        {
            this.ResourceType = ResourceManager_Fields.RESOURCE_TEMPLATE;
        }

        /**
         *  gets the named resource as a stream, parses and inits
         *
         * @return true if successful
         * @throws ResourceNotFoundException if template not found
         *          from any available source.
         * @throws ParseErrorException if template cannot be parsed due
         *          to syntax (or other) error.
         * @throws IOException problem reading input stream
         */
        public override bool Process()
        {
            data = null;
            Stream _is = null;
            errorCondition = null;

            /*
             *  first, try to get the stream from the loader
             */
            try
            {
                _is = resourceLoader.GetResourceStream(name);
            }
            catch (ResourceNotFoundException rnfe)
            {
                /*
                 *  remember and re-throw
                 */

                errorCondition = rnfe;
                throw rnfe;
            }

            /*
             *  if that worked, lets protect in case a loader impl
             *  forgets to throw a proper exception
             */

            if (_is != null)
            {
                /*
                 *  now parse the template
                 */

                try
                {
                    StreamReader br = new StreamReader(_is, Encoding.GetEncoding(encoding));
                    data = rsvc.Parse(br, name);
                    InitDocument();
                    return true;
                }
                catch (ArgumentException uce)
                {
                    String msg = "Template.process : Unsupported input encoding : " + encoding
                    + " for template " + name;

                    errorCondition = new ParseErrorException(msg);
                    throw errorCondition;
                }
                catch (ParseException pex)
                {
                    /*
                     *  remember the error and convert
                     */
                    errorCondition = new ParseErrorException(pex, name);
                    throw errorCondition;
                }
                catch (TemplateInitException pex)
                {
                    errorCondition = new ParseErrorException(pex, name);
                    throw errorCondition;
                }
                /**
                 * pass through runtime exceptions
                 */
                catch (ApplicationException e)
                {
                    errorCondition = new VelocityException("Exception thrown processing Template "
                        + Name, e);
                    throw errorCondition;
                }
                finally
                {
                    /*
                     *  Make sure to close the inputstream when we are done.
                     */
                    try
                    {
                        _is.Close();
                    }
                    catch (IOException e)
                    {
                        // If we are already throwing an exception then we want the original
                        // exception to be continued to be thrown, otherwise, throw a new Exception.
                        if (errorCondition == null)
                        {
                            throw new VelocityException(e);
                        }
                    }
                }
            }
            else
            {
                /*
                 *  is == null, therefore we have some kind of file issue
                 */
                errorCondition = new ResourceNotFoundException("Unknown resource error for resource " + name);
                throw errorCondition;
            }
        }

        /**
         *  initializes the document.  init() is not longer
         *  dependant upon context, but we need to let the
         *  init() carry the template name down throught for VM
         *  namespace features
         * @throws TemplateInitException When a problem occurs during the document initialization.
         */
        public void InitDocument()
        {
            /*
             *  send an empty InternalContextAdapter down into the AST to initialize it
             */

            InternalContextAdapterImpl ica = new InternalContextAdapterImpl(new VelocityContext());

            try
            {
                /*
                 *  put the current template name on the stack
                 */

                ica.PushCurrentTemplateName(name);
                ica.CurrentResource = this;

                /*
                 *  init the AST
                 */

                ((SimpleNode)data).Init(ica, rsvc);

                String property = scopeName + '.' + RuntimeConstants.PROVIDE_SCOPE_CONTROL;
                provideScope = rsvc.GetBoolean(property, provideScope);
            }
            finally
            {
                /*
                 *  in case something blows up...
                 *  pull it off for completeness
                 */

                ica.PopCurrentTemplateName();
                ica.CurrentResource = null;
            }

        }

        /**
         * The AST node structure is merged with the
         * context to produce the final output.
         *
         *  @param context Conext with data elements accessed by template
         *  @param writer output writer for rendered template
         *  @throws ResourceNotFoundException if template not found
         *          from any available source.
         *  @throws ParseErrorException if template cannot be parsed due
         *          to syntax (or other) error.
         *  @throws MethodInvocationException When a method on a referenced object in the context could not invoked.
         */
        public void Merge(IContext context, TextWriter writer)
        {
            Merge(context, writer, null);
        }


        /**
         * The AST node structure is merged with the
         * context to produce the final output.
         *
         *  @param context Conext with data elements accessed by template
         *  @param writer output writer for rendered template
         *  @param macroLibraries a list of template files containing macros to be used when merging
         *  @throws ResourceNotFoundException if template not found
         *          from any available source.
         *  @throws ParseErrorException if template cannot be parsed due
         *          to syntax (or other) error.
         *  @throws MethodInvocationException When a method on a referenced object in the context could not invoked.
         *  @since 1.6
         */
        public void Merge(IContext context, TextWriter writer, IList macroLibraries)
        {
            /*
             *  we shouldn't have to do this, as if there is an error condition,
             *  the application code should never get a reference to the
             *  Template
             */

            if (errorCondition != null)
            {
                throw errorCondition;
            }

            if (data != null)
            {
                /*
                 *  create an InternalContextAdapter to carry the user Context down
                 *  into the rendering engine.  Set the template name and render()
                 */

                InternalContextAdapterImpl ica = new InternalContextAdapterImpl(context);

                /**
                 * Set the macro libraries
                 */
                ica.MacroLibraries = macroLibraries;

                if (macroLibraries != null)
                {
                    for (int i = 0; i < macroLibraries.Count; i++)
                    {
                        /**
                         * Build the macro library
                         */
                        try
                        {
                            rsvc.getTemplate((String)macroLibraries[i]);
                        }
                        catch (ResourceNotFoundException re)
                        {
                            /*
                            * the macro lib wasn't found.  Note it and throw
                            */
                            rsvc.getLog().error("template.merge(): " +
                                    "cannot find template " +
                                    (String)macroLibraries[i]);
                            throw re;
                        }
                        catch (ParseErrorException pe)
                        {
                            /*
                            * the macro lib was found, but didn't parse - syntax error
                            *  note it and throw
                            */
                            rsvc.getLog().error("template.merge(): " +
                                    "syntax error in template " +
                                    (String)macroLibraries[i] + ".");
                            throw pe;
                        }

                        catch (Exception e)
                        {
                            throw new ApplicationException("Template.merge(): parse failed in template  " +
                                    (String)macroLibraries[i] + ".", e);
                        }
                    }
                }

                if (provideScope)
                {
                    ica.Put(scopeName, new Scope(this, ica.Get(scopeName)));
                }
                try
                {
                    ica.PushCurrentTemplateName(name);
                    ica.CurrentResource = this;

                    ((SimpleNode)data).Render(ica, writer);
                }
                catch (StopCommand stop)
                {
                    if (!stop.isFor(this))
                    {
                        throw stop;
                    }
                    else if (rsvc.getLog().isDebugEnabled())
                    {
                        rsvc.getLog().debug(stop.Message);
                    }
                }
                catch (IOException e)
                {
                    throw new VelocityException("IO Error rendering template '" + name + "'", e);
                }
                finally
                {
                    /*
                     *  lets make sure that we always clean up the context
                     */
                    ica.PopCurrentTemplateName();
                    ica.CurrentResource = null;

                    if (provideScope)
                    {
                        Object obj = ica.Get(scopeName);
                        if (obj is Scope)
                        {
                            Scope scope = (Scope)obj;
                            if (scope.Parent != null)
                            {
                                ica.Put(scopeName, scope.Parent);
                            }
                            else if (scope.Replaced != null)
                            {
                                ica.Put(scopeName, scope.Replaced);
                            }
                            else
                            {
                                ica.Remove(scopeName);
                            }
                        }
                    }
                }
            }
            else
            {
                /*
                 * this shouldn't happen either, but just in case.
                 */

                String msg = "Template.merge() failure. The document is null, " +
                    "most likely due to parsing error.";

                throw new ApplicationException(msg);

            }
        }
    }
}
